.TH std::stop_token::stop_possible 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::stop_token::stop_possible \- std::stop_token::stop_possible

.SH Synopsis
   [[nodiscard]] bool stop_possible() const noexcept;  \fI(since C++20)\fP

   Checks if the stop_token object has associated stop-state, and that state either has
   already had a stop requested or it has associated std::stop_source object(s).

   A default constructed stop_token has no associated stop-state, and thus cannot be
   stopped; the associated stop-state for which no std::stop_source object(s) exist can
   also not be stopped if such a request has not already been made.

.SH Parameters

   \fI(none)\fP

.SH Return value

   false if the stop_token object has no associated stop-state, or it did not yet
   receive a stop request and there are no associated std::stop_source object(s); true
   otherwise.

.SH Notes

   If the stop_token object has associated stop-state and a stop request has already
   been made, this function still returns true.

   If the stop_token object has associated stop-state from a std::jthread—for example,
   the stop_token was retrieved by invoking get_stop_token() on a std::jthread
   object—then this function always returns true. A std::jthread always has an internal
   std::stop_source object, even if the thread's invoking function does not check it.

.SH Example


// Run this code

 #include <chrono>
 #include <condition_variable>
 #include <format>
 #include <iostream>
 #include <mutex>
 #include <string_view>
 #include <thread>
 using namespace std::chrono_literals;

 int main()
 {
     std::cout << std::boolalpha;
     auto print = [](std::string_view name, const std::stop_token& token)
     {
         std::cout << std::format("{}: stop_possible = {:s}, stop_requested = {:s}\\n",
             name, token.stop_possible(), token.stop_requested()
         );
     };

     // A worker thread that will listen to stop requests
     auto stop_worker = std::jthread([](std::stop_token stoken)
     {
         for (int i = 10; i; --i)
         {
             std::this_thread::sleep_for(300ms);
             if (stoken.stop_requested())
             {
                 std::cout << "  Sleepy worker is requested to stop\\n";
                 return;
             }
             std::cout << "  Sleepy worker goes back to sleep\\n";
         }
     });

     // A worker thread that will only stop when completed
     auto inf_worker = std::jthread([]()
     {
         for (int i = 5; i; --i)
         {
             std::this_thread::sleep_for(300ms);
             std::cout << "  Run as long as we want\\n";
         }
     });

     std::stop_token def_token;
     std::stop_token stop_token = stop_worker.get_stop_token();
     std::stop_token inf_token = inf_worker.get_stop_token();
     print("def_token ", def_token);
     print("stop_token", stop_token);
     print("inf_token ", inf_token);

     std::cout << "\\nRequest and join stop_worker:\\n";
     stop_worker.request_stop();
     stop_worker.join();

     std::cout << "\\nRequest and join inf_worker:\\n";
     inf_worker.request_stop();
     inf_worker.join();
     std::cout << '\\n';

     print("def_token ", def_token);
     print("stop_token", stop_token);
     print("inf_token ", inf_token);
 }

.SH Possible output:

 def_token : stop_possible = false, stop_requested = false
 stop_token: stop_possible = true, stop_requested = false
 inf_token : stop_possible = true, stop_requested = false

 Request and join stop_worker:
   Run as long as we want
   Sleepy worker is requested to stop

 Request and join inf_worker:
   Run as long as we want
   Run as long as we want
   Run as long as we want
   Run as long as we want

 def_token : stop_possible = false, stop_requested = false
 stop_token: stop_possible = true, stop_requested = true
 inf_token : stop_possible = true, stop_requested = true
